An investigation into side stream technologies as a potential solution for reducing nitrogen emissions from municipal waste waters in the Irish situation

摘要

This study explicated the requirement to substantially increase the level of nutrient removaludfacilities at municipal waste water treatment plants on a national scale. This requirement hasudresulted from recently enacted legislation. The research then considered the options forudrealisation of these infrastructural improvements.udRevolutionary methods of nitrogen reduction have been established and developed, whichudtarget nitrogen-rich side streams from sludge handling processes, for more sustainableudnitrogen removal from the main process effluents. Dundalk WWTP was chosen as a caseudstudy site, to assess the viability of applying these new technologies in Ireland, and toudprovide comparison with conventional means. An evaluation o f the nitrogen mass balance atudDundalk showed that 45.7% of the main plant total nitrogen load is contained within theudammonium-rich recycle effluents, currently returned untreated to the headworks.udApproximately 20% Total Nitrogen reduction is possible at this facility through side streamudtreatment application.udTwo options for side stream treatment were assessed; based on efficiency predictions, bothudsystems would shift the operation of the B-stage treatment process at Dundalk from oxygenudlimited to ammonium limited, reducing the Total Nitrogen emissions to within acceptableudlimits. When compared against conventional biological nitrogen removal processes,udapplying a unitary operational cost driver, the cost of conventional treatment is significantlyudgreater than the side stream options examined. Reduction of nitrogen in a side streamudtreatment process is more sustainable and energy efficient than nitrogen reduction in audconventional stream.udThis study demonstrated that certain side stream technologies exist, which can provide anudeconomically viable option for the various Irish plants requiring such reduction in emissions,udwhilst reducing the carbon footprint of these facilities. For this reason, the potential use ofudside stream technology should be afforded due consideration on a national scale.udPilot plant installation in advance of full-scale implementation at Dundalk is recommended.udAn opportunity for further study also exists in determining the suitability of this technologyudfor sustainable phosphorus removal from waste waters and for leachate pre-treatment.